1. Field
The present invention relates generally to communications. More particularly, in aspects the invention relates to an energy-saving indicator in a transmission frame.
2. Background
Portability and functionality of wireless communication devices continue to improve, contributing to the proliferation of wireless communication networks. Many conventionally-wired connections are being replaced with wireless connections, including ad hoc connections made when one wireless device moves into the connectivity area of another wireless device. Of some interest are wireless personal area networks (wireless PANs or WPANs), which are networks that are often used for communications between or among devices close to one person. The reach of a PAN is typically of the order of ten meters, although some networks operate over distances three or even ten times as long. A personal area network may be used for communications between or among personal devices, or for communications between such personal devices and higher level networks, including the Internet. A wireless personal area network may be implemented using ultra-wide band (UWB) technologies.
ECMA-368 is a high rate physical (PHY) layer and medium access control (MAC) standard promulgated by ECMA International for UWB communications. This standard is based on the WiMedia UWB Common Radio Platform. At this time, the latest version of the ECMA-368 standard is the 2nd edition dated Dec. 2007.
Portable devices are typically battery-powered. Energy conservation is therefore important in such devices for keeping the batteries small without unduly compromising battery life.
Substantial energy may be expended in a portable device keeping the device's radio frequency receiver operational during times when no transmissions are directed to the device. Although the receiver may be turned off between transmissions, the precise times of incoming data are not always known in advance. Transmission times may also not be susceptible to prediction, even on the transmitter side, because the MAC layer of the transmitter may not be able to predict data flow from a given application. One technique for receiver energy conservation is for the transmitter to inform the receiver whether to expect additional transmissions during the current transmission period. The use of a simple flag (as defined in the ECMA-368 standard) to signal the receiver that no transmissions will be made for a period create a conflict between energy conservation and the ability to accommodate bursty and asynchronous data sources. If new data from the application becomes available for transmission shortly after the transmitter signals that no additional transmissions will be made, then data latency and buffer overrun probability at the transmitter may increase.
A need exists in the art for apparatus, methods, and articles of manufacture that improve energy efficiency of wireless receivers. A need also exists for apparatus, methods, and articles of manufacture that decrease latency of wireless transmissions and reduce or eliminate the probability of transmitter buffer overruns. A need further exists for apparatus methods, and articles of manufacture that allow reduction in the receiver on/off duty cycle and at the same time avoid excessive transmission latency and buffer overruns in wireless networks, including networks with devices having ECMA-368 PHY and MAC.